Electronic control in the wellhead area is now possible with 's intrinsically safe programmable logic controller
(ISPLC).

Conventional hydraulic and pneumatic control panels are replaced by electronic controllers local to each wellhead.

The ISPLC also monitors wellhead data for transmission to the platform's distributed control system.

Benefits are:

Cable and piping installation is dramatically reduced

Significant overall platform weight reduction

Installation and hook up time is reduced

System expansion to meet additional wells

Each ISPLC will control two single or one dual completion well. The PLC drives intrinsically safe solenoid valves
within a hydraulic interface unit to operate the sub sea, master and wing valves.

Cost Benefit

Typical cost benefit for a 20 well platform compared with conventional hydraulic control panels.

Weight

50%

Capital Cost

60%

Installation hook up time

50%

Significant benefits also exist in lifetime maintenance and support

Connection in the wellhead areas is minimised to common high and low pressure hydraulic headers, and return line, two
wire electrical data bus and electrical power linking all wellhead controllers.

The wellhead ISPLC undertakes:

Logical sequencing including process and platform shutdowns.

Safety interlocks

Timing

Choke valve control

Pressure flow and status monitoring

Local manual valve control, including emergency shutdown is provided.

Control Logic

The logic system ensures safety valves operate in the correct sequence. Adjustable time delays and interlocks are
incorporated. High and low level alarms for any measurement are available. The ISPLC will communicate with the
platform DCS via a standard PLC gateway, or can operate stand alone.

Safety

The ISPLC is designed to fail freeze/safe. Power failure will cause solenoids to release so that valves close, with
hydraulic sequencing for the down hole safety valve. All solenoid valves have manual control to enable continued
production during maintenance.

Emergency Shutdown

The system can be interlocked with central fire and gas or ESD systems to initiate shutdown. High-low flowline pressure
sensors enable pipework to be protected from high pressures and line breaks.

Overrides are available for workover and wirelining purposes.

Choke Valve

If required each ISPLC will control upto two choke valves with:

Auto bean up

Variable ramping and crackpoint transition optimisation

Alternate direction of opening

Flow calculations (AGA)

Specification

The system has 8 control outputs nominally for 3 valves, expandable to operate 6 for dual completion, with capacity
for 3 choke valves and with valve position and flowline pressure monitoring.